Improvement of breakdown and flashover properties against thermal aging of oil paper insulation through addition of TiO ₂ nanoparticles

Abstract

TiO 2 nanoparticles can improve the electrical performance of oil paper insulation. In this study, 10 nm TiO 2 nanoparticles were prepared and dispersed into transformer oil, and then immerse pressboards in it to obtain nanofluid impregnated pressboards (NP). Its thermal aging was accelerated together with the reference sample at 130 • C for 36 days. Analyzing the acid value in the oil, polymerization degree, surface topography, AC breakdown strength, surface flashover characteristics and surface potential decay characteristics. It was observed that TiO 2 nanoparticles can reduce the acid value and improve AC breakdown strength of oil. However, the degree of polymerization and surface appearance of NP and oil impregnated pressboards (OP) during thermal aging did not differ significantly. During the aging process, the energy level of pressboard surface traps shifted first towards the shallow and then gradually towards the deep. During all the aging stages, the surface flashover voltage of NP was always higher or close to that of OP. The mechanism of TiO 2 nanoparticles improving the breakdown and surface flashover characteristics of oil-paper insulation during thermal aging is discussed from the perspective of water molecules and aging by-products adsorption and introduction of shallow traps by nanoparticles.